The present invention relates to a tubular shaft instrument, in particular a trocar, having an instrument channel which can be closed off by a flap valve, and having an actuation element for opening the flap valve against the force of a closing spring.
A tubular shaft instrument of this kind in the form of a trocar is known from DE 39 23 243 C2.
The flap valve contains a flap which, in the closed state, extends perpendicular to the instrument channel. The flap is pivotable about a pivot axis laid alongside the instrument channel, and is pushed in the closing direction by the force of a closing spring.
The actuation element for opening the flap valve consists of an annular disk which surrounds the instrument channel and is axially displaceable in the direction of the instrument channel axis. The disk is joined to the flap of the flap valve via a plunger extending along the instrument channel axis. The plunger is arranged alongside the instrument channel, and encounters the closed flap valve in a region adjacent to the pivot axis or the hinge axis on which the flap valve is articulated. To open the flap valve, the actuation element is displaced axially so that the plunger is also axially displaced and pushes the flap valve up. The instrument channel is now open, so that an instrument, for example a trocar mandrel or an endoscope, can be slid through the trocar. A spring presses the released actuation element back into its initial position, and the flap valve then pivots in the closing direction until it encounters the inserted instrument. Depending on the configuration of the exterior of the instrument, the latter can simply be withdrawn, after which the flap valve is pressed back into the closed position because of the closing spring and closes off the instrument channel. The result is that, for example when instruments are being changed, no gases or fluids can emerge through the instrument channel from the body into which the trocar has been introduced. If the flap valve lying against the instrument should first be moved away from the latter in order to withdraw the instrument, the actuation element is once again axially displaced and the flap valve is again pivoted via the plunger into its maximum open position.
This design requires a relatively large installation space alongside the actual instrument channel, and in the case of small trocars (for example pediatric trocars) leads to unnecessarily protruding sizes. With many tubular shaft instruments it is moreover desirable to require as little radial width as possible in terms of the usable open inside diameter of the instrument channel.
DE 70 04 051 U1 discloses a trocar sleeve whose instrument channel can also be closed off via a flap valve.
A cylinder mounted with limited displaceability, which rests with its one annular end surface on the closed flap, is provided in order to open the flap. A slotted plastic spring washer is placed in the interior of the cylinder.
If a trocar mandrel is now placed into the trocar sleeve, its tip encounters the slotted spring washer, penetrates partially through it, and thereby expands it slightly until sufficient frictional engagement has been created so that further advancing of the trocar mandrel distally displaces the displaceably mounted cylinder which carries the slotted spring washer. The distal end of the cylinder thereby pushes up the flap of the flap valve. Because the cylinder can be slid forward over only a limited distance, it strikes against a stop, so that further advancing of the trocar mandrel causes the slotted spring washer to be opened sufficiently wide that the trocar mandrel can be displaced distally farther into the instrument channel. Upon withdrawal, the trocar mandrel pulls the cylinder back again until it strikes against a stop. As a result, the spring-loaded flap can swing in again and close off the instrument channel.
This design requires instruments matched exactly to the cylinder, in order to ensure the frictional engagement necessary for the movement sequence. If the frictional engagement between instrument and slotted spring washer is insufficient, the instrument can pass through the cylinder without displacing it and thus without causing the flap valve to open, which instead must be done by the inserted instrument; in the case of a trocar mandrel, which has a very sharp tip, this can lead to damage or jamming. If the instrument is too large as a result of production tolerances, jamming takes place between the instrument and the cylinder, thus interfering with the movement sequence.
It is an object of the present invention to develop a tubular shaft instrument of the kind cited initially in such a way that the opening and closing movements of the flap valve can be controlled in an easily handled manner using means of simple design which require little space.